Process for emulsification and demulsification by surfactants and the recovery thereof



PROCESS FOR EMULSIFICATION AND FICATION BY SURFACTANTS AND THE RE- COVERY THEREOF Harold L. Greenwald, Levittown, Pa., assignor to Rohm & Haas Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Filed Sept. 15, 1958, Ser. No. 760,935 2 Claims. (Cl. 252-303) This invention relates to a novel process for forming and resolving or separating oil-water type emulsions. It is especially significant because it also provides for the reclamation and reuse of the emulsifying agent.

There are numerous areas in which the invention is applicable. One is the recovery operation in oil produc- 1 tion which is considerably improved by the use of my' accomplish the oil recovery, and for recovering and reusing most of the surfactant so used.

Another object is to provide a process for the recovery of oil by the use of an aqueous surfactant solution which causes an oil-water emulsion to be produced said emulsion being readily and inexpensively broken so that the United States Patent DEMULSI- flooding operation or a strip-mining operation in both of which an aqueous surfactant solution is employed to surfactant can be efiicientlyrecovered in a single phase and reused and the oils economically obtained.

Other objects of the invention, together with some of the advantageous features thereof, will appear from the following description and specification. In most cases, recovery of the surfactant willbe a principal feature; however, the invention is not necessarily limited thereto as in certain applications it will be useful only to emulsify and demulsify in accordance with the novel methods herein described.

Many agents have been proposed for emulsifying and demulsifying oils. But in certain applications notably in the recovery of oil from various unusual petroluem-bearing formations, such as tar sands, these agents have proven unsatisfactory for one reason or another. principal objections are the use of relatively costly emulsifying materials which are substantially non-recoverable, the difiiculty in forming the emulsions, the difiiculty in breaking the emulsions, etc. a

The present invention overcomes all of these objections by the novel use of certain surfactants in the emulsification-demulsification procedures which make possible, high recovery of all components by controllably changing the hydrophile-lipophile balance of a surfactant during the process. (The terms surfactant and emulsifier or emulsifying agent as hereinafter employed may be used interchangeably.) The controlled change of this balance is brought about by the use of pH-sensitive emulsifiers:

The oil is either emulsified under alkaline conditionsand the emulsion later broken by adding acid to make the solution acidic, or emulsified under'acid conditions and broken by adding alkali to make the solution alkaline. In actual practice, it may be desirable in some cases to effect a closer control of the acidity of alkalinity of the treated Among the q 3,102,100 Patented Aug. 27,1 963 reuse is facilitated either by preferential solulbility'of the surfactant in the organic or the aqueous plias'e or by precipitation of the surfactant. My invention may. thus be practiced in three alternative procedures which may conveniently be grouped as follows:

CATEGORY A (l) Make oil-water emulsion by means of. a surfactant (2) Recover surfactant in aqueous phase by suitable control of pH in both steps i a CATEGORY B p (1) Make oil-water emulsion by means of a surfactant (2) Recover surfactant in organic phase by suitable control of pH in both steps CATEGORY C As indicated earlier, and as will be explained in more detail below, the emulsions formed'in each of the above categories may optionally be made in a base and broken with an acid, or vice versa.

Ordinarily, in emulsions, appreciable fractions of the total emulsifier are found in three locations: (1) the bulk oil; phase; (2) the bulk aqueous phase; andl'(3) in :the region of the interface. In my invention, 1 not only destroy the emulsion, but also I elfect a concentration of the surfactant in one bulk phase or theaother as I choose. This choice is made dependent on the contemplated mode of reuse of the surfactant or of the surfactant solution. In some cases, I may choose to concentrate a surfactant as a separate, pure-or almost pure-phase for convenience in reuse. This ability to concentrate, in one phase, a good emulsifier which otherwise is spread over three locations as above explained, is a novel as well as highly useful feature of my invention.

EXAMPLES OF PROCESS. EMPLOYING SINGLE CYCLE Not all surfactants will work in my novel process and, of those that do work, not all of them will function satisfactorily in each of the three categories described above. The selection and manner of employment of the various surfactants are, therefore, import-ant tothe successful practice of the invention. In essence, it may be stated that any surfactant having weakly acidic or weakly basic groups will work in one or more of the systems encompassed by my invention. The surfactants which will not work efficiently are those whose hydrophilic portion is entirely (a) non-ionic, or (b) composed of the anion of .a strong acid or of the cation of a strong base.

In the numerous examples which were conducted to demonstrate the operation of the invention, the star-ting solutionsemployed were divided into two main sets. One set was a 0.5 percent solution of the surfactant in 0.5 percent NaOH; and the other set was a 0.5 percent solution of the surfactant in 0.5 percent H However, in order to demonstrate effectiveness at different concentrations, several experiments were run in which the initial surfactant concentration ranged from 0.05 to 20 percent.

Equal volumes of the oil and of the surfactant-caustic or of the surfactantacid solution (as the case may he) were placed in each of two screwacap jars and agitated on a reciprocating type shaker for 15 minutes. The emulsified contents of one jar were poured into a graduated cylinder and allowed to stand for one hour, at which time the volumes of the various phases were recorded and the percent recovery of the aqueous phase (a measure of emulsion instability) computed. To the contentsot the other jar either acid or base was added until the pH was precipitated upon acidification, the surfactant qualified rendered 'below about in the ones which were made for category C. The same principles were usedm deacidic and above around '9 in the ones which were made termining the utility of surfactants for the processes in alkalineg After a complete breaking of the emulsion, each of the three categories in which the oil was emulsior after vone hour, whichever was earlier, the volumes of 5 fied in acid and broken with base, except that the direction the. organic and aqueous phases, respectively, were realong the'pH seale was reversed. corded. Suitable surfactants for the particular oil-water 1 'The above-described tests involved in a single cycle system gave low instability in the first jar and high inprocess, and the data obtained thereby are representedin stability in the second jar. The emulsion instability one Tables 1, 2, 3, and 4. Other experiments were run with hour-after adding the 'acid or base 'was computed and rea recycling process, which will be described "111 detail ported as the percent recovery of the aqueous phase. below, and the data obtained thereby are represented 1n For any surfactant having weakly acidic or weakly Tables 5, "6, and 7. In almost all of the examples, the basic groups, oil-water systems will be found in which oils used were toluene andVentura crude oil (a relarmy invention operate efficiently. Conversely, for .tively clean crude oil). Six other oils (i.e., organic any given oil-water system, surfactants "of this-type exist liquids which are insoluble in water"); were used to test which willwo rk efiiciently. It is well known in the art the eificiency of the invention under various conditions that the hydrophile-lipophile balance of an emulsifier demaking a total of eight as follows:

. tor-mines its eifectiveness for a given oil-water system.

-.The surfactants which formed a relatively stable emulsion v (1) Toluene Thus, the well-known techniques for choosing a good Venmm crude oil g emulsifier are to be applied to the classes containing Howard Glasscock crude e k1 cidic or weakly Ibasic groups as a preliminary (4) Hawkins Field crude il step in the practice of my invention. This was done as Wesson 011 (cottonseed il described in the following para-graphs. I i (6) ppbm l b t vAll the tests were conducted at room temperature. (7)-Di octy1sebacate The pH avas checked at two or more points in each case. Mixture of lauryl i myristyl alcohols in base were deemed to be useful in the processes of all Nora-Nos. 2, 3, and 4 represent oils that are well three categories, A, B, and C, previously described, parknown by those names to persons familiar with the ticularly the :processes in'which the oilwas emulsified in petroleum field. No. 5 is a well-known commercial prod- ;baseand broken with acid. High, low, or moderate reuct sold under that name. No. 8 is a commercially availcovery of the surfactant in the aqueous phase determined able mixture sold under a trade name.

'whether the surfactant belonged in category .A or B or. w The results obtained with the single cycle process are failed to qualify.. If a high percentageof thesurfactant set forth inTables 14.

Table 1 EMULSIFIED IN CAUSTIC, BROKEN WITH ACID; SURFACTANI RECOVERED IN AQUEOUS PHASE I Organic phase: Toluene Aqueous phase: Surfactant, 0.5% NaOH, deionized H2O (all pHs-z 12.8-13.1)

Surfactant 1 Emulsion (A) percent (B) percent Mole ratio cone. in Emulsion pH 6 after instability of LC. of of LC. of Surfactant otEO (n) l w./v.% instability acidifiafter surfactant surfactant (AH-(B) (I.C.) in caustic cation acidifiin aqueous in toluene cation I n=nu1 nber of units of ethylene oxide, including the ethanol termination, in the polyether chain.

b 1.0. =in1t1al concentration of surfactant expressed as weight/volume percent. c A single result such as 3 or 3.0 denotes that all of the data were taken for this one pair of emulsions. Where a range 18 indicated, such as 2-4, one of them (the 2 or the 4) was a repeat. The figures not reported to a tenht of a pH unit were determined by using pH test papers; the other figures were obtained with a pH meter.

d (Al-H15) should equal 100 percent for complete accountability of the surfactant. Result pbtamcd was greater than 100 percent due to limitations of method of analysis caused by the low concentration of the surfactant. I s

4 'NOTES ON TABLE 1 {(1 Surfactants Nos. "1-8 were ethylene oxide adducts of a commercial product. comprisinl a mixture of amines which i (3). Surfactant No. 11 was a commercially available product,

principally covers therange o CnHzsNHa 'llOCrcHaaNH2, the l number "of ethylene oxide units per amine being from 10 whm'eas Table 1 comauns data companng vanous I" to 30. 1 a (2), Surfactants Nos, 910were each the sodiu m salt of the mutants d emulslficatlon-demulsifiea m y 'sulf'ated ethylene oxide add-nets of the type referred to in note (1) above. in which only toluene was employed, Table 2 which folg. dehydroabietylamine ethylene oxide adduct with the :10Ws compared surfactants in the process as applied to structure V KCHzCHOhH 7 various other oils.

RN I

(CH2OH20) H g in which a:+y: 20.' y 5 (1) Surfactants Nos, 1-7 and 14-17 were the same as de .Surfiactwt 13 was Table 2 EMULSIFIED IN CAUSTIC, BROKEN WITH ACID; SURFAC'IANT RECOVERED IN AQUEOUS PHASE Organicphase: Various Oils Listed Aqueous phase: Surfactant, 0.5% NaOH, deionized H O Mole ratio Surfactant Emulsion pH() after Emulsion Percent of Surfactant of E0 (n) conc.1n W./ Oil used instability acidificainstability LC of sury.% (1.0.) l in caustic tion after acidiiactant in fication aqueous 12. 6 0. 5 Venltura crude 56 6. 6 9O 01 15.0 0.05 4 3-4 96 15.0 0.5 44 3. 4 98 99 15. 0 5. 0 8 3. 0 100 93 20. 0 O. 5 40 4. 0-5. 5 101 20.0 20. 0 0 1. 4 95 99 i 30.0 0.5 40 2.4-4 100 0. 5 22 4. 0 75 15 O. 5 54 2.6 Y 100 25 0.5 62 2. 5 96 15 0. 5 44 2.9 100 50 0.5 60-70 2 93 20 0. 5 46 2. 6 98 15 0.5 59 2-3 99 9;) 15 0. 5 53 2-3 97 89 20 0.5 Wesson oil- 79 2 100 20 5.0 doi 50 2 94 98 20 0.5 Mixture of 0 2.1 0-32 lauryl and myristyl alcohols.

H Same as note inTable 1. b Same as note in Table 1.

6 Same as note in Table 1. t The Venture crude oil contains some impurities which were extracted into the aqueous phase in some ins ances.

8 Same as note in Table 1.

NOTES ON TABLE 2 in which w+y:15; the Hatter has the same structure except that w+y=50.

a commercially available product,

a dehydroabietylamine ethylene oxide adduct with the structure scribed in note (1) in Table 1 (2 sqi ng'aciimt No. 8 was the same as described in note (2) in a e (3) Surfactants Nos 9-10 were ethylene oxide adducts of a mixture of amines which principally covers the range of C1'I-24H35-4BNH2 where the number of ethylene oxide units (CHQCHIQXH per amine is 15 and 25 respectively. (4) Surfactants Nos. 11-12 were a coco-amine e'tnylene oxide adduct, and a stearyl-amine ethylene oxide adduct, .respectively. The formers structure is (CHzCHzO),H

(CHflCH2 )x i m which :v-l-yzZO. R-N (6) Surfactant No. 18 was sodium P-t-OC'tYIIYhEHOXYFOIYGthoxy (20 units) acetate with the structure (CH2CH2O),,H

Table 3 EMULSIFIED IN CAUSTIC, BROKEN SURFACTANT RECOVERED AS PRE- Organic phase: Toluene (except for item marked by asterisk in which Ventura crude oil was used) Aqueous phase: 0.5% surfactant, 0.5% NaQH, deionized water Emulsion Emulsion pH after Percent of Percent of Percent of Surfactant W instability Material instability acidifica- LC. in 1.0. in LG. which in caustic added after aciditicn aqueous toluene precipification tated HuSO4 2. 1 14 14 107 H2804..- 100 2 4 29 29 51 H2304"... ca. 100 4. 0 12 94 H 804"-.- 92 4 Same as note in Table 1. Same as note in Table 2.

NOTES ON TABLE 3 l (2) Surfactant N0. 2 was disod-ium jBJauryLiminodipropionate. (1) Surfactant No. 1 was disodium fi tallow 'iminodipro- (3)'Surfactants Nos. 3 and 4 were sodium B-coco amino pionate. v propionate.

Table 4 EMULSIFIED IN ACID, BROKEN WITH BASE; SURFACTANT RECOVERED IN AQUEOUS OR ORGANIC PHASES Organic phase: Toluene (except for items marked by asterisk in which Ventura crude oil was used) Aqueous phase: 0.5% surfactant, 0.5% H 80 deionized water (all pHs: 1-2) Emulsion Mole ratio Emulsion Material instability pH after Percent of Percent of Surfactant of E instability added after adding LC. in 1.0. in (11) in acid adding material aqueous toluene material 100 5 0 NaOH 78 11.4 23 6 100 NaOH 11. 4 4 5 0 NaOH. 100 13. 2 30 7. 5 100 7. 5 0 NaOH. 11. 6 9 NaOH. 10 20 48 NaOH 83 13. 3 12 18 NaOH 102 12.7 108 I Same as note in Table I.

NOTES ON AB 4! vary, depending upon the scale on WhlCh my invention is (1) The results with surfactants 1-6 inclusive show the different effects with different oils. Note that 'Wllth Ventura crude the same surfactant that worked well in Nos. 2 and 4 did not work at all with toluene in Nos. 1 and 3. Similarly, with Ventura crude in No. 6, a good result was obtained, but in No. 5 toluene did not work at all.

(2) Surfactants Nos. 1-6 were the same as described in note (1) in Table 1.

'(3) Surfactants Nos. '7-8 were the same as described in note (6) in Table 2. r

('4) Surflactant No. 9 was sodium N-polyeiihoxy (11 11111135) ethyldodecenylsuccinamate.

In the examples shown in Tables 1 to 4, the number of 4 units of ethylene oxide employed in the amine-E0 adducts therein specified ranged from 10-30 in some cases and from 15-50 in others. Actually, these are merely illustrative. It is possible to use compounds having from about 5 to about 100 units per amine group, depending upon the particular oil and water combination of interest.

EXAMPLES OF PROCESS EMPLOYING CONTINUOUS CYCLES From the foregoing tables, it was apparent that" among the surfactants which may be employed in the inventive process, one of the most successful types isthe group 5 comprising a number of amine-ethylene oxide adducts. Of these, the products, identified as an ethylene oride adduct (15-30 units) of a commercial product comprising a mixture of amines which principally covers the range'T-C H NH to T-CHHZQNHZ excelled all other surfactants tested in several oil-water systems when consideration was given to emulsion stability in caustic solution, cfficiently (time'and completeness) of breaking, and recoverability of the surfactant. One of them (the one having 15units of ethylene oxide) was therefore selected for a series of recycling experiments in which the same batch of caustic-surfactant solution was used repeatedly to form the emulsion, then reclaimed, freed of most of the inorganic salt, and used again to emulsify a fresh 0 batch of the same oil. The number of cycles in each experiment was limited only by the fact that the volume of emulsion was constantly being decreased as samples were removed for determination of emulsion stability in caustic solution and for analysis. This type of limitationw-ill forth in Tables 5-8. They were obtained by the following. procedure:

Equal volumes of oiland of a 0.5 percent caustic-0.5 percent surfactant solution .(500 cc. of each phase at the start) were vigorously mixedby a mechanical shaker for 15 minutes. A control sample of the emulsion was withdrawn for measuring emulsion stability in caustic," allowed to stand for an hour, and the phase volumes read. The remaining emulsion was poured into a graduated separatory funnel and dilute H 50 added until the emulsion broke and .the pH was below 5, shaking well after adding each increment. The completeness of breaking (i.e., percent recovery of oil) was determined.

A sample of the aqueous phase (and of the organic phase in the case of toluene) was withdrawn and analyzed for surfactant. An amount of Ca(OH) equivalent to the H present was added to the solution. The solution was shaken for a few minutes, then filtered to remove the precipitate. A sufficient amount of NaOH was then added to raise the pH to that of the starting solution, viz., 12.8-12.9.

Failure to remove CaSO, prior to replenishing caustic would result in the redissolving of some CaSO and such removal is therefore preferable. (If other alkaline materials are used in lieu of the Ca(OH) this problem does not occur. Optionally, also, HCl [or any other inorganic acid, or organic acid, or acid salts] could be used instead of H 80 and other alkaline materials can also be used. The I-ICl and NaOH will form NaCl which can be allowed to accumulate or may be removed by some other means without interfering with the process.) The Ca(-OH) precipitated by the NaOH was eliminated by refiltration. The volume of the filtrate was measured and an equal volume of fresh oil added thereto, after which all of the foregoing steps were repeated a number of times as shown in Tables 5-8.

Tables 5-8 set forth data obtained when the cyclic process was applied to each of four diiferentoils, using one of the preferred surfactants (the one having 15 units of ethylene oxide as an adduct of T-C H 'NH as aforesaid.

Table 5 TOLUENE Emulsion pH after Emulsion Percent of Cumula- Percent of umula- Cycle N0. instability acidificainstability 1.0. in tive per- I.0.1n tivepcrcent in Control tion after acid- H1O cent of toluene of 1.0. 111

ification 1.0. toluene 40 2. 9 (100) (102. 5) (102. 5) (0. 6) (o. 0) 51 2.1 101 99. 8 102.2 0 0. a 39 2. e 100 98.0 100.2 0 0. 6 28 2. 2 100 98. 5 98. 7 0. 6 1. 2 50 2. 4 100 100. 8 99. 4 3.8 5. 0 50 2.8 97.6 97.0 0.6 5.7 49 2. 7 101 101.0 98. 0 -0. 7 5. 0 64 2.2 102 100.0 98.0 2.9 7.8

a 1.0.? is initial concentration.

Table 6 Percent recovery of organic phase after acidification:

Toluene 100. VENTURA CRUDE OIL Ventura, Glasscock, i Emulsion pH after Percent of Cumulative Hawkms In nearly all cases, the volume Cycle No. instability acidification 1.0. in percent of of black upper phase was a 160mm 1 H20 little greater than the vol- 99 .ume of pure oil available. 52 3.5 (8g) The interface was not dis- 76 2 109 2g :cernible, so the exact per- 3 2 82 'centages of pure oil and water-in-oil emulsion could a 1.0. is initial concentration. not be detemlllled- Average percent recovery of surfactant into aqueous Table 7 Phase- Toluene 100 HOWARD GLASSCOCK CRUDE OIL Ventura 94 i t E U1 P t f C u] Glasscock 94 Emulsion Hat er in sion ereen o um av I Cycle instability gcidificainstability I. o. in tivef iorocent Hawkms p 91 32 ,35? m0 40 CONCLUSIONS AND OBSERVATIONS The foregoing description has clearly demonstrated 64 (96) (96) (96) the efiicient manner in which my invention can be em- 99 2.8 100 99 95 0 3.4 80 99 94 ployed to emulsify and demulsify 011s, and provide for 88 91 100 94 the reclamation and reuse of the emulsifying agent.

72 2.8 94 90 85 54. 2.7 94 93 79 This is done either by adding to the 011 a base in a sur- 94 100 93 74 .factant solution-and then breaking the emulsion by adding acid, or by adding acid in a surfactant solution and o-"islmtialconcentratwnbreaking the emulsion by adding a base. I he applications of the invention are manifold, whether employed in Table 8 a single cycle or a continuous processing operation.

Mention has been made of the practice of the invention HAWKINS FIELD CRUDE OIL in connection with the recovery of oil. Such oil recovery, i i which in itself is not new, is practiced in a number of Cycle Emulsion pH after Emulsion lierentof t Cl1ml1 fl-t ways. One common practice involves the drilling of adl Q n 0 I a n I 1 1 1 iih t i i fi ibii mo 53}??? acentholes deep mm the ground, then mecting a flushing fication material mto one hole to force the oil out of another. In the past, water containing a surfactant has been used 30 3.1 (g2) (g3) ($8) for this flushing operation. It is understood that a more 2% 3: 97 90 71 recent development involve-s the use of a mixture of a 93 gt; 3? surfactant such as a t-octylphenol ethylene oxide adduct 3?, 99 9g 56 and a caustic solution. The principal purpose of this 8 g3 g2 g2 flushing procedure has been to emulsify oils which were 5 contained in petroleum producing formations, and the a I. 0. is initial concentration.

Some of the more salient points reflected by the recycling data in Tables 5-8 may be summarized as follows.

Average percent recovery of aqueous phase after acidilike, which could not be broken loose and flushed out by pre-existing procedures. But the method has thus far not proven to be commercially acceptable because it has been diflicul t and expensive to break the emulsion thus formed, and the surfactant has not been recoverable. My invention has overcome this objection and now makes it possible to employ this eflicient and economical technique for the recovery of many billions of gallons of oil that heretofore were relatively inaccessible from a commercial standpoint.

It will be apparent to most chemists that the invention 9 can be applied to numerous other situations where it is plus NaCl, plus Na CO The emulsion which results is acidified, causing it to break. The grease and surfactants are each recovered in their respective, separate phases which are formed thereby.

Likewise, the invention could be applied to fracturing gels. The function of such a :gel is to serve as a vehicle for sand, the resulting slurry being used to fracture or porifiorate rigid silicious oil-bearing formations. After fracturing formation, the presence of the gel is no longer desired. The gel may be formed by the use of an emulsifier such as t-C H NH (EO) containing a built-in emulsion breaker such as benzotrichloride which decomposes slowly to liberate H01. The acid eventually lowers the pH of the solution to the point where it causes the gel to break.

Still another application would be to clean out the holds of oil tankers, etc. The oil and tars remaining in the holds could be emulsified by pumping in the caustic-surfactant solution, then acidified in situ (or after transferring the emulsion to another hold) to break the emulsion and make recovery of the surfactant possible.

A further application would be in the preparation of rapid-breaking asphalt emulsions. In this use, of course, recovery of the surfactant is not contemplate-d; but the ease and speedof emulsion-breaking made possible by the invention are the main factors .Which favor its use.

A still further application is in connection with destructible foaming agents for air drilling. In such cases, the surfactants "would be recoverable.

It is obvious, therefore, that the possible applications of my invention are widespread. It is thus appropriate that the invention should not be limited in its scope to just the few examples and other data given hereinabove but instead should be construed in the light of the claims which follow.

1 claim: 1 1. A cyclic process for emulsifying an oil-water system and reusing theemulsifying agent in the process, which comprises the steps of emulsifying an oil under alkaline conditions by the addition of :a pH-sensitive surfactant and water thereto, said surfactant being selected from'the class 12 in which R is a dehydroabietyl group and x1y,=15 to 50, i and subsequently breaking the emulsion by addition of an acidic substance so as to make the oil-Water system acidic to thereby concentrate the surfactant in a bulk phase, and recycling said bulk phase in said process so asto emulsify more oil as aforesaid.

.2 A cyclic process for emulsifying an oil water systern and reusing the emulsifying agent in the process,

which comprises the steps of emulsifying an oil under acid conditions by the addition of a pH-sensitive surfactant and water thereto, said surfactant being selected from the class consisting of: (a) the ethylene oxide adducts of a range of amines represented by the formula C H NH where the number of ethylene oxide units is from 5 to 50 per amine; I

C H NH(C H O) SO Na Where "=3 to 50; and 1 in which R is a dehydroabietyl' group and x+y=l5 to 50, and subsequently breaking the emulsion by addition of an alkaline substance so as to make the oil-watersystem alkaline to thereby concentrate the surfactant in a bulk phase, and recycling said bulk phase in said process so as to emulsify more oil as aforesaid.

References Cited in the file of this patent UNITED STATES PATENTS 2,215,624 istrezynski Sept. 24, 1940 2,270,411 Campbell Jan. 20, 1942 2,296,459 Schutte Sept. 22, 1942 2,354,856 Erwin Aug. 1,1;1944 2,605,272 Hunn et a1. July 29, 1952 2,662,062 Sumerford Dec. 8, 1953 2,784,161 Foley i Mar. 5-, 1957 2,800,962 Garst July 30, 1957 2,802,785 Nowak Aug. '13, 1957 2,874,779 'Johnson Feb. 24, 1959 2,882,973 Doscher et a1. Apr. 21, 1959 OTHER REFERENCES The Chemistry of Fatty Amines, published by AI- mour and Co., 1948, pp. 1-5, 17 and 18. 

1. A CYCLIC PROCESS FOR EMULSIFYING AN OIL-WATER SYSTEM AND REUSING THE EMULSIFYING AGENT IN THE PROCESS, WHICH COMPRISES THE STEPS OF EMULSIFYING AN OIL UNDER ALKALINE CONDITIONS BY THE ADDITION OF A PH-SENSITIVE SURFACTANT AND WATER THHERETO, SAID SURFACTANT BEING SELECTED FROM THE CLASS CONSISTING OF: (A) THE ETHYLENE OXIDE ADDUCTS OF A RANGE OF AMINES REPRESENTED BY THE FORMULA C11-24H23-49NH2 WHERE THE NUMBER OF ETHYLENE OXIDEE UNITS IS FORM 5 TO 50 PER AMINE; (B) C11-24H23-49NH(C2H4O)NSO4NA WHERE N=3 TO 50; AND 